Too dog tired to avoid danger: Self-control depletion in canines increases behavioral approach toward

posted Oct 13, 2009, 12:58 AM by Charles Henderson   [ updated Apr 22, 2012, 6:43 PM ]
Too dog tired to avoid danger: Self-control depletion in canines increases behavioral approach toward
an aggressive threat.
 


Holly C. Miller & C. Nathan DeWall & Kristina Pattison &

Mikaël Molet & Thomas R. Zentall

# Psychonomic Society, Inc. 2012



Abstract
 
This study investigated whether initial selfcontrol

exertion by dogs would affect behavioral approach

toward an aggressive threat. Dogs were initially required to

exert self-control (sit still for 10 min) or not (caged for

10 min) before they were walked into a room in which a

barking, growling dog was caged. Subject dogs spent 4 min

in this room but were free to choose where in the room they

spent their time. Approaching the unfamiliar conspecific

was the predisposed response, but it was also the riskier

choice (Lindsay, 2005). We found that following the exertion

of self-control (in comparison with the control condition),

dogs spent greater time in proximity to the aggressor.

This pattern of behavior suggests that initial self-control

exertion results in riskier and more impulsive decision making

by dogs.
 


Keywords Self-regulation . Dogs . Decision making . Risk

taking . Impulsivity

The potential for danger is ubiquitous. To avoid danger, people

often exert self-control over their behavior (Baumeister, 1998;

Baumeister, Heatherton & Tice, 1994). When people fail to

exert self-control and behave more impulsively, they may

unintentionally put themselves in harm’s way (Freeman &

Muraven, 2010). Pedestrians jaywalk across busy streets,

children stick objects into electrical outlets, and teenagers

join dangerous gangs. The failure to exert self-control

and avoid these dangerous activities is likely affected by

many individual variables (e.g., demographics, personality).

However, a common mechanism that may be responsible for

human and nonhuman self-control vigor may also play a role

(Miller, Pattison, DeWall, Rayburn-Reeves & Zentall, 2010).

The present research tested this hypothesis by examining

whether dogs approach dangerous situations when their ability

to exert self-control is compromised.

Research with human and nonhuman animals suggests

that self-control relies on a limited resource (Baumeister &

Heatherton, 2004; Miller et al., 2010). Exerting self-control

depletes this resource, and once depleted, subsequent efforts

to control behavior become impaired. For example, when

humans control their impulse to eat fresh cookies (in comparison

to when they inhibit eating radishes), they then

persist for a shorter time on an unsolvable puzzle task

(Baumeister, Bratslavsky, Muraven & Tice, 1998). Dogs

behave similarly. When dogs control their physical movement

(in comparison with when self-control is not needed

because they are physically constrained by a cage), they

persist for a shorter duration on a subsequent unsolvable

puzzle task (Miller et al., 2010).

Extensive research with humans suggests that this phenomenon

is domain general, suggesting that tasks that require selfcontrol

negatively affect performance on a wide variety of

subsequent tasks (for a review, see Baumeister, Schmeichel &

Vohs, 2007). Decision making, for example, is negatively

affected by initial self-control exertion. Depleted subjects, as

compared with their nondepleted counterparts, take more risks

and gamble more (Bruyneel, DeWitte, Franses & Dekimpe,

2009; Freeman & Muraven, 2010; Molet, Miller, Laude, Kirk,

Manning & Zentall, 2012). To date, however, there is no

evidence that initial self-control exertion affects subsequent

H. C. Miller (*) : M. Molet

Université de Lille, Nord de France,

Domaine universitaire du “Pont de Bois”, Rue du Barreau,

BP 60149, 59653 Villeneuve d’Ascq Cedex, France

e-mail: hcmiller1661@gmail.com

C. N. DeWall : K. Pattison : T. R. Zentall

University of Kentucky,

Lexington, KY, USA

Psychon Bull Rev

DOI 10.3758/s13423-012-0231-0



behavior in more than one domain for nonhuman animals, nor

is there evidence that depleted humans or nonhuman animals

are more likely to inadvertently subject themselves to risks that

may result in physical harm.

Some recent evidence suggests this possibility, because

self-regulatory depletion increases approach motivation

(Schmeichel, Harmon-Jones & Harmon-Jones, 2010) and

behaviors with an approach-related motivational direction,

such as aggression (Denson, Pedersen, Friese, Hahm &

Roberts, 2011; DeWall, Baumeister, Stillman & Gailliot,

2007; Finkel, DeWall, Slotter, Oaten & Foshee, 2009).

Consequently, the purpose of the present investigation was

to determine whether self-regulatory depletion has domaingeneral

consequences on nonhuman animal behavior and to

examine the likelihood that depletion would cause dogs to

put themselves in harm’s way by approaching a physically

threatening target. We chose dogs, in part, because, like

humans, they are highly social animals that establish social

dominance hierarchies and need to be sensitive to social

cues provided by other members of their species.

We adopted a two-task procedure used widely in the

human self-control literature (Baumeister, Bratslavsky,

Muraven & Tice, 1998). Dogs were tested twice, individually,

and we varied the requirements of the first task between

sessions. In the first task, either the dog was required to sit

still for 10 min (self-control depletion), or the movement of

the dog was constrained by placing it inside of a cage for the

same duration (control). Next, the dog was brought into a

room in which it encountered a caged, barking, and growling

dog. Dogs spent time in this room, but their behavior

was unconstrained. Thus, dogs could choose to spend their

time near the aggressor, or they could stay farther away.

Although dogs are predisposed to approach and investigate

unknown conspecifics (Lindsay, 2000), in this context, it

was the more dangerous thing to do. Greater proximity to a

confined aggressive dog, despite the confinement, is associated

with a greater risk of an aggressive encounter (American

Veterinary Medical Association, 2011; Lindsay, 2001, 2005;

Sacks, Sattin & Bonzo, 1989). Consequently, staying near the

aggressor was defined as the riskier (more impulsive) choice,

and avoidance was defined as the safer (less impulsive)

choice. We predicted that self-control depletion, as compared

with the control condition, would increase approach-related

behavior toward the threatening dog.

Method

Subjects

We recruited 10 dogs (Canis familiaris; 4 males, 6 females)

ranging from 12 to 120 months of age (M 0 48.8 months).

All dogs belonged to private owners, would immediately

approach a friendly caged dog, and had been trained to

maintain an out-of-sight sit–stay for 10 min. They had also

been trained to remain calm inside a cage for as long as 6 h.

Apparatus

A bath mat was placed on the floor in front of an empty dog

cage (1.2 m long × 0.8 m wide × 0.9 m high) that was

surrounded by a ProSelect™ exercise pen (see Fig. 1). The

dogs sat on this mat during the self-control manipulation.

This mat was placed inside a second dog cage (0.9 m long ×

0.6 m wide × 0.7 high) at the same location during the

control condition. A mirror was placed strategically on the

wall so that the experimenter could watch the dogs from

outside of the room through a small opening in the door. To

increase the difficulty of the self-control depletion phase, an

electronic “hamster” (Zhu Zhu pets®) was placed inside an

Adventure Ball™ and was activated inside the room during

the self-control depletion phase (see Fig. 1).

A highly dominant dog (an 11-year-old female bull terrier)

with a disposition for guarding territory was placed in a

dog cage (1.2 m long × 0.8 m wide × 0.9 m high) that was

surrounded by the ProSelect™ exercise pen. This dog

would bark and growl continuously whenever it was confined

and another dog was visible. The intensity of this

display was greater when its owner was close by, suggesting

that the dog included its owner as part of its territory to

defend (Borchelt, 1983; Lindsay, 2001). For this reason, the

owner (O) stood next to the dog during testing.

Fig. 1 The experimental room as it was set up for the self-control

manipulation that preceded the impulsivity test

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For safety reasons, the pen that was placed around the cage

provided an additional distance of 0.3 m between the aggressive

dog and the subject dog. The room (3.9 m long × 3.8 m

wide) was demarcated into zones by lines made with Scotch®

masking tape (2.5 cm wide; see Fig. 2). The first of four lines

was 61 cm from the screen (zone 1), and zone was 61 cm deep

(zones 2, 3, and 4). Because there were doors in zones 1 and 4

and standing near a door should be considered an escape

behavior rather than an approach behavior, we chose to define

this zone separately. The dog was considered in door space if

its front two feet were within 30 cm of the door and the dog's

body was pointing in the direction of the door.

In the first phase of the experiment, the door (B) was left

slightly ajar; however, both doors were closed during the

second phase of the experiment. Two video cameras were

used to record each testing session; one was mounted on a

tripod to the left of the aggressive dog, and an experimenter

who was to the right of the dog operated the other camera.

Procedure

Pretesting At least 1 week before testing, all subject dogs

were introduced to a friendly caged dog. All subject dogs

approached the caged dog upon being released from leashed

restraint. The purpose of this testing was to ensure that

subject dogs were predisposed to approach an unknown

conspecific and that some level of inhibition would be

required for avoidance. In addition, subject dogs were

leashed and were exposed to the Zhu Zhu® hamster to

ensure that they were interested in but not frightened by it

when it moved. This assessment eliminated the possibility

that fear would confound the self-control manipulation.

Testing All dogs were tested with both conditions of the

self-control manipulation (order was counterbalanced). In

the self-control depletion condition, the dog was cued to

“sit” and “stay” by Experimenter 1 (E1). Following the cue,

E1 activated the Zhu Zhu® hamster and exited the room

through door A while the dog maintained its position. The

hamster was used to increase the difficulty of the selfcontrol

task. With the door slightly ajar, E1 watched the

dog (without being seen by the dog) via a strategically

placed mirror. The dog was allowed to keep visual track of

the hamster but if the dog moved from its position, E1

returned and gave the sit–stay cue again. A second experimenter

(E2), who stood outside of the testing room (behind

door A), recorded the number of cues and the time at which

each cue was given. The dog remained alone in the room

with the electronic hamster for a total of 10 min.

When the dog was released, it was given a small piece of

wiener (1 g), was moved to an adjacent room, and was

praised for 30 s by E1. After the subject dog left the testing

room, the aggressive dog was led into the newly vacant

room through door B by its owner (O) who was blind to

the self-control manipulation. The aggressive dog was

placed inside the cage, and O stood next to the cage behind

the exercise pen during testing. Once the aggressive dog was

situated, E1 entered the room with the subject dog (which

caused the aggressive dog to start barking and growling),

quietly walked the subject dog across the room on leash, and

unleashed it at a predesignated spot without further interaction

(black dot in Fig. 2). E1 then filmed the subject dog’s

behavior for 4 min while quietly standing still and looking at

the dog only via the screen of the digital camera. At the end

of 4 min, E1 leashed the subject dog and removed it from

the experimental room through door B.

In the control condition, E1 placed the subject dog inside

a dog cage and was told by E2 to return to the dog and

“recue” it to get inside of the cage at the same times she had

previously cued the dog during the self-control condition. If

the dogs’ first test session was in the control condition, it

was revisited by E1 three times at minutes 1, 5, and 7 during

the 10 min. This was the average number of revisits required

in a previous experiment (Miller et al., 2010). During the

control condition, the electronic hamster was inside the

room but was not activated. Pilot research indicated that

the hamster attracted attention from dogs during the sit–stay

but that, when activated while caged, it caused some dogs to

whine, circle, and paw. The remaining procedural variables

were held constant between conditions. Dogs were tested

between the hours of 09:00 and 15:00. A video clip displaying

the dogs’ behavior during the control manipulation

can be found at http://www.youtube.com/watch?

v0849mWDrXnC8.

An observer, who was blind to the subjects’ condition,

Fig. 2 The experimental room as it was set up for the impulsivity test used a digital stopwatch to time the duration that subject

Psychon Bull Rev



dogs spent in each zone. A second blind observer coded

10% of the observations to obtain a reliability measure.

There was a positive Pearson correlation between the two

observers, r 0 .99, p < .01.

Results

The dogs responded differently in the two conditions. The

dogs generally spent more time in zone 1 and near the doors,

especially following the self-control condition. The proportion

of time spent in each zone and near the door appears in Fig. 3.

A two-way repeated measures analysis of variance

(ANOVA) analyzed the differences of time spent in the

zones (+doors) across conditions (self-control, control).

Time spent in the room did not differ as a function of

condition because total time was equated, but the time spent

in the zones was significantly different, F(4, 36) 0 5.06, p <

.01, and the dispersion of time spent in zones was significantly

affected by self-control condition, F(4, 36) 0 2.56,

p 0 .05. Subsequent analyses were run to examine the

observed differences. A one-way repeated measures

ANOVA examining the effect of zone for the self-control

condition found that there was a very reliable effect of zone

following self-control exertion, F(4, 51) 0 6.08, p < .01, but

not following the control condition, F(4, 51) 0 1.88, p 0 .13.

When the simple effects of zone within each condition (selfcontrol,

control) were analyzed, it was observed that following

self-control exertion, dogs reliably spent more time in

zone 1 than in 2, 3, and 4, F(9, 36) 0 13.29, 15.75, 16.17,

respectively, all ps < .01, but not more time than near the

doors, F(9, 36) 0 3.67, p 0 .06. Following the control

condition, dogs did not spend a significantly different

amount of time between zones 1 and 2, F(9, 36) 0 2.13,

p 0 .15, but they did spend a significantly greater time in

zone 1 than in zones 3 and 4, F(9, 36) 0 5.67, 5.54, all

ps 0 .02. Here again, time spent in zone 1 did not differ from

time spent at the doors, F(9, 36) 0 1.95, p 0 .17.

Planned comparisons using two-tailed correlated samples

t-tests were performed on the difference scores in each zone

between the two conditions. The difference was significant

in zone 1, t(9) 0 3.11, p 0 .01 (dogs spent more time in zone

1 following the self-control condition), and in zone 2, t(9) 0

2.39, p 0 .04 (dogs spent more time in zone 2 following the

control condition), but it was not significant in either of the

other two zones (or near the doors), all ts < 1.2. As was

predicted, self-control depletion caused dogs to spend a

greater percentage of time in the zone nearest to the aggressive

dog (58.9%), as compared with the control condition

(41.8%). The data from individual dogs in both the selfcontrol

and control conditions appear in Fig. 4.

Discussion

Avoiding danger enhances an animal’s ability to survive and

reproduce. Yet there are often occasions when the need to

avoid danger is paired with a natural tendency to approach.

To keep out of harm’s way, animals override their natural

impulse to approach in order to remain safe and secure.

When animals have limited self-control resources, they

may make more impulsive decisions that put them in harm’s

way. The present experiment examined whether initial exertion

of self-control would increase impulsivity in dogs,

resulting in risky decisions.

Our results supported this prediction. When dogs were

depleted, as compared with when they were not, they were

less able to inhibit their predisposed approach behaviors. As

a result, dogs approached an aggressive dog more when

depleted than when nondepleted.

Our interpretation of the present results rests on the

assumption that it is dangerous to approach a confined

aggressive dog and that subject dogs were risking their

safety by approaching. Although in the context of the present

experiment, strict precautions ensured the safety of all of

the dogs, confinement is not fail-proof in the natural world,

and it is quite possible that a confined aggressor could

escape and attack. Mail carriers are often attacked by presumably

confined dogs, as are children, and a significant

percentage of pet-related human fatalities result when a

restrained aggressive dog is approached (Sacks et al.,

1989; U.S. Postal Service, 2011). Moreover, moving away

from an aggressor defending its territory reduces the motivation

for attack (Lindsay, 2001).





present experiment, experimenters observed that the

aggressor displayed a more intense threat display when

subject dogs were near the fence and the intensity decreased

as subject dogs moved farther away. This observation

is similar to others regarding territorial behavior and

confinement (Calhoun, 1962; Klopfer, 1969; Lindsay,

2001; Pettijohn, Davis & Scott, 1980). It is also evidence

that approaching was relatively more risky than avoiding

the caged aggressor.

Another way of looking at the dogs’ behavior is as an

increase in counter aggression, provoked by the confined

aggressor. This complementary hypothesis is founded on

research demonstrating that humans, who typically suppress

emotionally driven aggressive responses, are more

likely to retaliate aggressively when they have depleted

their self-control. More specifically, when students initially

deplete their self-control by inhibiting their consumption

of a donut (but not a radish), they are less able

to control their aggressive behavior when they are subsequently

provoked (i.e., they are negatively evaluated

on a previously written essay). Depleted students retaliate

by adding more hot sauce to food intended for the

essay evaluator. Similarly, when students are initially

required to control their attention (inhibit reading words

displayed to them) and are subsequently given a negative

essay evaluation, they are more likely to administer

aversive noises to the essay evaluator. Furthermore,

following self-control exertion, students are more likely

to report the desire to inflict physical harm on someone

who provokes them (DeWall et al., 2007).

In the context of the present experiment, it is difficult to

delineate the role that increased aggression may have

played. Increased approach behavior may reflect counter

aggression, or it may reflect an increase in approach motivation.

Self-regulatory depletion increases approach motivation

in humans in the absence of aggressive intentions

and, thus, may have also contributed to the pattern of behavior

we observed in dogs (Schmeichel et al., 2010).

The commonality between human and nonhuman animals

is great, and the present research is further evidence

that human self-control has phylogenetic roots. It is also

further evidence that a phenomenon (i.e., depletion) once

believed to be uniquely human can be modeled with

dogs. Such modeling may have great empirical value,

since it may provide greater insight into the physiological

and neurobiological processes that affect self-control

vigor. Research with animal models will not supplant

that on cognitive factors involved in human selfregulation,

but it will augment our understanding of the

fundamental and biological rudiments of a phenomenon

that is clearly multifactorial in nature. Therefore, we

believe that social psychology will benefit by incorporating

work with nonhuman animals to extend existing

theories.



Author Note We thank Byron Nelson for his help with data analysis.

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